"I am not implying that I never mix colors or suggesting that you buy every color available to side step the need for mixing. Remember that color is most brilliant straight from the tube. Any two colors mixed produce a color less vibrant than either original unmixed color. Adding more color(s) further reduces vibrancy. Mixtures become muddied quickly when too many colors participate, especially if combining unlike hues (not close to each other on the color wheel). I prefer my colors mingled, not mixed. Brush marks of diverse color may be integrated without actually mixing them. At a short distance from the canvas, eyes deliver separated colors to the brain where they "seem" to mix ala-Seurat. Taking advantage of each color's inherent chromatic potency, the visual effect is much richer than looking at literally mixed, potentially muddy, versions. Note: This approach, while applicable to all color media, is particularly advantageous to oil painters. Avoiding unwanted wet into wet mixing keeps mud out of the picture."   
       - Caroline